In recent years, as the applications of the light-emitting diode increasing, many methods for increasing the light extraction efficiency have been provided. One of the methods is to reduce the electrical current crowding and make the electrical current spread between the electrodes wide. If the electrical current between the electrodes is not uniform and causes the electrical current crowded in some regions, the total light efficiency of the light-emitting diode will decrease.
In recent years, many methods have been provided to improve the light extraction efficiency of the light-emitting diode as the light-emitting diode is applied more widely. However, the current spreading in the light-emitting diode is not uniform so the current distribution is crowded in some areas, and there is a need to improve the light extraction efficiency
In order to make the current spreading uniform, a conventional LED structure has a current block region of low electric conductivity in the p-AlGaAs window layer to improve the current spreading and increase the light-emitting efficiency.
Referring to FIG. 1, a vertical type LED comprises a semiconductor stacked layer 12, a reflector layer 14 beneath the semiconductor stacked layer 12, and a conductive substrate 18 bonded to the reflector layer 14 by a bonding layer 16, wherein the semiconductor stacked layer 12 comprises an active layer 8, a first semiconductor layer 6 and a second semiconductor layer 10. A current block region 20 is often disposed in the vertical type LED to improve the current spreading. In general, the current block region 20 is often made of SiO2 and formed by photolithography and etching processes to be disposed in the semiconductor stacked layer 12. But, when the electric current is applied into the vertical type LED, the electrical current may gather around the corners of the current block region 20 to cause the high electric field. When the electric field strength is higher than the limit of the electric field loading of the LED, the LED fails. FIG. 2 shows the failed LED due to the high electric field occurring around the corner of the current block region 20, and a hole 21 is formed on the surface of the failed LED because of the high electric field.